Fair Value Measurements, Recurring (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Assets:
Commodity derivative contracts	$ 872	$ 537
Investments of certain benefit plans	110	109
Total gross fair value, assets	984	646
Commodity derivative contracts, net assets	89	25
Net Carrying Value on Balance Sheet, Assets	201	134
Cash Collateral Received Not Offset	0	0
Liabilities:
Commodity derivative contracts	792	516
Biofuels blending obligation	75	11
Foreign currency contracts	9	8
Total gross fair value, liabilities	877	540
Commodity derivative contracts, net liabilities	2	5
Net Carrying Value on Balance Sheet, Liabilities	87	29
Cash Collateral Paid Not Offset	(66)	(76)
Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts	2
Liabilities:
Physical purchase contracts	1	5
Fair Value, Inputs, Level 1 [Member]
Assets:
Commodity derivative contracts	709	499
Investments of certain benefit plans	99	98
Total gross fair value, assets	808	597
Liabilities:
Commodity derivative contracts	643	492
Biofuels blending obligation	0	0
Foreign currency contracts	9	8
Total gross fair value, liabilities	652	500
Fair Value, Inputs, Level 1 [Member] | Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts	0
Liabilities:
Physical purchase contracts	0	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Commodity derivative contracts	163	38
Investments of certain benefit plans	0	0
Total gross fair value, assets	165	38
Liabilities:
Commodity derivative contracts	149	24
Biofuels blending obligation	75	11
Foreign currency contracts	0	0
Total gross fair value, liabilities	225	40
Fair Value, Inputs, Level 2 [Member] | Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts	2
Liabilities:
Physical purchase contracts	1	5
Fair Value, Inputs, Level 3 [Member]
Assets:
Commodity derivative contracts	0	0
Investments of certain benefit plans	11	11
Total gross fair value, assets	11	11
Liabilities:
Commodity derivative contracts	0	0
Biofuels blending obligation	0	0
Foreign currency contracts	0	0
Total gross fair value, liabilities	0	0
Fair Value, Inputs, Level 3 [Member] | Physical Purchase Contracts [Member]
Assets:
Physical purchase contracts	0
Liabilities:
Physical purchase contracts	0	0
Netting [Member]
Assets:
Effect of Counterparty Netting	(759)	(505)
Effect of Cash Collateral Netting	(24)	(7)
Liabilities:
Effect of Counterparty Netting	(759)	(505)
Effect of Cash Collateral Netting	$ (31)	$ (6)